This invention is related to an apparatus and method for controlling the direction of a vehicle travelling through a fluid medium.
More particularly this invention constitutes a unique method and apparatus for actuating the aft control surfaces of a submarine with X-shaped empennage.
Most modern military submarines have a hull form that at least approximates an axisymmetric body of revolution. Most of these have four control surfaces at the stern for steering the vessel, that is, for making it turn left or right--the rudder--or rise or dive--diving plane--or a combination of both. In turn, in most modern submarines these control surfaces are in cruciform. That is, the rise-dive surfaces are generally in the same plane as the horizontal plane through the centerline of the vessel, and the turning surfaces are in the same plane as the vertical plane through the centerline. Thus, the control surfaces are generally in the form of a Greek cross.
In most cases the two rudder planes are yoked together, and the two diving planes are yoked together. Because of this yoking, each pair of control surfaces is operated by a single actuating rod. Thus, one rod turns the ship, and the other rod causes the ship to rise or dive.
It is known that arranging the control surfaces or planes of a submarine in an X configuration has certain advantages. In this form, the control surfaces are in the form of an X. Unlike cruciform designs, X-stern designs utilize all four planes as part of any maneuver. Therefore, an X-stern design enjoys more maneuvering force per unit of control surface area than cruciform designs. X-stern ships can be designed with smaller control surfaces while maintaining maneuvering envelopes comparable to cruciform ships with larger control surfaces. Smaller control surfaces obviously have less drag, but may also be quieter--a very important factor today for a submarine.
The submarine USS ALBACORE had an X-stern configuration where the opposite control surfaces were yoked together. Australian submarines of the recent COLLINS class have X-stern configurations, but the control surfaces are not yoked together and each of the four surfaces has its own actuator. These are two examples of the current known methods of actuating X-sterns. In both cases, the control system for the operating rods is more complicated than that aboard a cruciform ship. In a cruciform ship, if the helmsman wants to turn the ship, the control system commands the rudder operating rod to extend or retract. If a change in depth is required, the control system commands the diving operating rod to extend or retract. In both X-stern designs, the control system commands every operating rod to move in one direction or the other, for any maneuver. Controlling these coordinated operating rod movements is a complex task that can be accomplished with a computer. However, manual coordination of the operating rods, in the event of a computer casualty, is difficult.
Usually the turning axes of the control surfaces are perpendicular to the ship's centerline at the stern. In this configuration, yoking of the two planes on opposite sides of the ship is an option. Some X-stern configurations require that the turning axes of the control surfaces be tilted such that they are not perpendicular to the ship's centerline. In this case, the control surfaces cannot be yoked, since no two turning axes are collinear. For these designs, the only current method of actuation is to use four separate operating rods.
U.S. Pat. No. 3,757,720 gives some idea of the stern arrangement of a submarine. FIG. 2 of the patent shows the mechanism in the stern necessary to actuate the diving planes, including an additional mechanism to actuate a smaller control surface as part of the main surface. Another mechanism of the same type would be required to do the same for the rudder surfaces.
U.S. Pat. No. 2,654,334 shows a torpedo with four control surfaces. However, they are in cruciform and have actuating rods 29 and 32 and a control rod 26.
U.S. Pat. No. 5,186,117 shows an altogether different steering system for a submarine mounted at the bow; this patent is assigned to the assignee of the present invention.
An X-stern control surface actuation mechanism that requires only two and not four operating rods whether the planes on control surfaces are yoked or not is not known in the prior art but offers the following benefits:
a. The space in the stern of most submarines is filled with propulsion shafting and bearings, other equipment and piping, as well as for the control surface actuating mechanisms. Minimizing the number of control rods penetrating this space is highly desirable.
b. The operating rods would operate as they would be in a cruciform design. In other words, one rod would cause the ship to turn and the other rod would cause the ship to rise or dive. This would simplify the control system for the operating rods, and make manual operation of the operating rods as simple as it is in a cruciform design.